diff --git a/.github/scripts/windows_payment_checkout_smoke.ps1 b/.github/scripts/windows_payment_checkout_smoke.ps1
new file mode 100644
index 0000000000..6e7108d782
--- /dev/null
+++ b/.github/scripts/windows_payment_checkout_smoke.ps1
@@ -0,0 +1,1267 @@
+param(
+  [ValidateSet("orchestrator", "launcher")]
+  [string]$Mode = "orchestrator",
+  [string]$ServiceName = "LanternSvc",
+  [string]$InstalledAppPath = "C:\Program Files\Lantern\Lantern.exe",
+  [string]$InstalledDaemonPath = "C:\Program Files\Lantern\lanternd.exe",
+  [string]$ArtifactDirectory = "build/windows-payment-checkout-smoke",
+  [int]$WaitSeconds = 180,
+  [string]$ShepherdHostPattern = '(^|\.)m62mrsf\.com$',
+  [string]$LauncherConfigPath
+)
+
+$ErrorActionPreference = "Stop"
+$resolvedArtifacts = if ($Mode -eq "orchestrator") {
+  [System.IO.Path]::GetFullPath($ArtifactDirectory)
+} else {
+  $null
+}
+$serviceDataDirectory = Join-Path $env:ProgramData "Lantern\payment-smoke-data"
+$serviceLogDirectory = Join-Path $env:ProgramData "Lantern\payment-smoke-logs"
+if ($resolvedArtifacts) {
+  New-Item -ItemType Directory -Path $resolvedArtifacts -Force | Out-Null
+}
+
+Add-Type -AssemblyName UIAutomationClient
+Add-Type -AssemblyName UIAutomationTypes
+Add-Type -AssemblyName Accessibility
+Add-Type -AssemblyName System.Drawing
+Add-Type -AssemblyName System.Windows.Forms
+
+function Initialize-NativeSmokeHelpers {
+  if ("WindowsPaymentSmoke.NativeToken" -as [type]) {
+    return
+  }
+
+  $accessibilityAssembly = [Accessibility.IAccessible].Assembly.Location
+  Add-Type -ReferencedAssemblies $accessibilityAssembly -TypeDefinition @'
+namespace WindowsPaymentSmoke {
+  public static class NativeMouse {
+    [System.Runtime.InteropServices.DllImport("user32.dll")]
+    public static extern void mouse_event(
+      uint flags, uint dx, uint dy, uint data, System.UIntPtr extraInfo);
+  }
+
+  public static class NativeToken {
+    private const uint PROCESS_QUERY_LIMITED_INFORMATION = 0x1000;
+    private const uint TOKEN_QUERY = 0x0008;
+    private const int TokenElevation = 20;
+
+    [System.Runtime.InteropServices.StructLayout(
+      System.Runtime.InteropServices.LayoutKind.Sequential)]
+    private struct TOKEN_ELEVATION {
+      public int TokenIsElevated;
+    }
+
+    [System.Runtime.InteropServices.DllImport("kernel32.dll", SetLastError = true)]
+    private static extern System.IntPtr OpenProcess(
+      uint access, bool inheritHandle, int processId);
+
+    [System.Runtime.InteropServices.DllImport("advapi32.dll", SetLastError = true)]
+    private static extern bool OpenProcessToken(
+      System.IntPtr processHandle, uint access, out System.IntPtr tokenHandle);
+
+    [System.Runtime.InteropServices.DllImport("advapi32.dll", SetLastError = true)]
+    private static extern bool GetTokenInformation(
+      System.IntPtr tokenHandle,
+      int tokenInformationClass,
+      out TOKEN_ELEVATION tokenInformation,
+      int tokenInformationLength,
+      out int returnLength);
+
+    [System.Runtime.InteropServices.DllImport("kernel32.dll")]
+    private static extern bool CloseHandle(System.IntPtr handle);
+
+    public static bool IsElevated(int processId) {
+      System.IntPtr process = OpenProcess(
+        PROCESS_QUERY_LIMITED_INFORMATION, false, processId);
+      if (process == System.IntPtr.Zero) {
+        throw new System.ComponentModel.Win32Exception();
+      }
+      try {
+        System.IntPtr token;
+        if (!OpenProcessToken(process, TOKEN_QUERY, out token)) {
+          throw new System.ComponentModel.Win32Exception();
+        }
+        try {
+          TOKEN_ELEVATION elevation;
+          int returned;
+          if (!GetTokenInformation(
+              token,
+              TokenElevation,
+              out elevation,
+              System.Runtime.InteropServices.Marshal.SizeOf<TOKEN_ELEVATION>(),
+              out returned)) {
+            throw new System.ComponentModel.Win32Exception();
+          }
+          return elevation.TokenIsElevated != 0;
+        } finally {
+          CloseHandle(token);
+        }
+      } finally {
+        CloseHandle(process);
+      }
+    }
+  }
+
+  public static class NativeAccessibility {
+    private const uint OBJID_CLIENT = unchecked((uint)-4);
+    private const int CHILDID_SELF = 0;
+    private const uint MOUSEEVENTF_LEFTDOWN = 0x0002;
+    private const uint MOUSEEVENTF_LEFTUP = 0x0004;
+
+    private sealed class Match {
+      public Accessibility.IAccessible Container;
+      public object ChildId;
+    }
+
+    [System.Runtime.InteropServices.DllImport("oleacc.dll")]
+    private static extern int AccessibleObjectFromWindow(
+      System.IntPtr window,
+      uint objectId,
+      ref System.Guid interfaceId,
+      out Accessibility.IAccessible accessible);
+
+    [System.Runtime.InteropServices.DllImport("oleacc.dll")]
+    private static extern int AccessibleChildren(
+      Accessibility.IAccessible container,
+      int childStart,
+      int childCount,
+      [System.Runtime.InteropServices.In,
+       System.Runtime.InteropServices.Out,
+       System.Runtime.InteropServices.MarshalAs(
+         System.Runtime.InteropServices.UnmanagedType.LPArray,
+         SizeParamIndex = 2)]
+      object[] children,
+      out int obtained);
+
+    [System.Runtime.InteropServices.DllImport("user32.dll")]
+    private static extern bool SetCursorPos(int x, int y);
+
+    [System.Runtime.InteropServices.DllImport("user32.dll")]
+    private static extern System.IntPtr GetAncestor(
+      System.IntPtr window, uint flags);
+
+    [System.Runtime.InteropServices.DllImport("user32.dll")]
+    private static extern bool SetForegroundWindow(System.IntPtr window);
+
+    public static bool ContainsName(
+        System.IntPtr window, string targetName) {
+      Accessibility.IAccessible root = Root(window);
+      if (root == null) {
+        return false;
+      }
+      int visited = 0;
+      return Find(root, targetName, 0, ref visited) != null;
+    }
+
+    public static bool ClickByName(
+        System.IntPtr window, string targetName) {
+      Accessibility.IAccessible root = Root(window);
+      if (root == null) {
+        return false;
+      }
+      int visited = 0;
+      Match match = Find(root, targetName, 0, ref visited);
+      if (match == null) {
+        return false;
+      }
+
+      try {
+        string action =
+          match.Container.get_accDefaultAction(match.ChildId);
+        if (!string.IsNullOrWhiteSpace(action)) {
+          match.Container.accDoDefaultAction(match.ChildId);
+          return true;
+        }
+      } catch (System.Runtime.InteropServices.COMException) {
+      }
+
+      int left;
+      int top;
+      int width;
+      int height;
+      try {
+        match.Container.accLocation(
+          out left, out top, out width, out height, match.ChildId);
+        if (width > 0 && height > 0) {
+          System.IntPtr topLevel = GetAncestor(window, 2);
+          if (topLevel != System.IntPtr.Zero) {
+            SetForegroundWindow(topLevel);
+          }
+          if (!SetCursorPos(
+              left + (width / 2), top + (height / 2))) {
+            return false;
+          }
+          NativeMouse.mouse_event(
+            MOUSEEVENTF_LEFTDOWN, 0, 0, 0, System.UIntPtr.Zero);
+          NativeMouse.mouse_event(
+            MOUSEEVENTF_LEFTUP, 0, 0, 0, System.UIntPtr.Zero);
+          return true;
+        }
+      } catch (System.Runtime.InteropServices.COMException) {
+        return false;
+      }
+      return false;
+    }
+
+    public static string DescribeNames(System.IntPtr window) {
+      Accessibility.IAccessible root = Root(window);
+      if (root == null) {
+        return "(MSAA root unavailable)";
+      }
+      System.Collections.Generic.List<string> names =
+        new System.Collections.Generic.List<string>();
+      int visited = 0;
+      CollectNames(root, names, 0, ref visited);
+      int rootChildren;
+      try {
+        rootChildren = root.accChildCount;
+      } catch (System.Runtime.InteropServices.COMException) {
+        rootChildren = -1;
+      }
+      string description = names.Count == 0
+        ? "(no named MSAA elements)"
+        : string.Join(", ", names.ToArray());
+      return string.Format(
+        "rootChildren={0}; visited={1}; names={2}",
+        rootChildren,
+        visited,
+        description);
+    }
+
+    private static Accessibility.IAccessible Root(System.IntPtr window) {
+      System.Guid accessibleId = new System.Guid(
+        "618736E0-3C3D-11CF-810C-00AA00389B71");
+      Accessibility.IAccessible accessible;
+      int result = AccessibleObjectFromWindow(
+        window, OBJID_CLIENT, ref accessibleId, out accessible);
+      return result >= 0 ? accessible : null;
+    }
+
+    private static Match Find(
+        Accessibility.IAccessible container,
+        string targetName,
+        int depth,
+        ref int visited) {
+      if (container == null || depth > 64 || visited >= 5000) {
+        return null;
+      }
+      visited++;
+      if (NameEquals(container, CHILDID_SELF, targetName)) {
+        return new Match {
+          Container = container,
+          ChildId = CHILDID_SELF,
+        };
+      }
+
+      object[] children = Children(container);
+      foreach (object child in children) {
+        Accessibility.IAccessible childAccessible =
+          child as Accessibility.IAccessible;
+        if (childAccessible != null) {
+          Match match = Find(
+            childAccessible, targetName, depth + 1, ref visited);
+          if (match != null) {
+            return match;
+          }
+          continue;
+        }
+        if (child != null && NameEquals(container, child, targetName)) {
+          return new Match {
+            Container = container,
+            ChildId = child,
+          };
+        }
+      }
+      return null;
+    }
+
+    private static void CollectNames(
+        Accessibility.IAccessible container,
+        System.Collections.Generic.List<string> names,
+        int depth,
+        ref int visited) {
+      if (container == null || depth > 64 ||
+          visited >= 5000 || names.Count >= 100) {
+        return;
+      }
+      visited++;
+      AddName(container, CHILDID_SELF, names);
+      foreach (object child in Children(container)) {
+        Accessibility.IAccessible childAccessible =
+          child as Accessibility.IAccessible;
+        if (childAccessible != null) {
+          CollectNames(childAccessible, names, depth + 1, ref visited);
+        } else if (child != null) {
+          AddName(container, child, names);
+        }
+      }
+    }
+
+    private static object[] Children(
+        Accessibility.IAccessible container) {
+      int childCount;
+      try {
+        childCount = container.accChildCount;
+      } catch (System.Runtime.InteropServices.COMException) {
+        return new object[0];
+      }
+      if (childCount <= 0) {
+        return new object[0];
+      }
+
+      object[] children = new object[childCount];
+      int obtained;
+      int result = AccessibleChildren(
+        container, 0, childCount, children, out obtained);
+      if (result < 0 || obtained <= 0) {
+        return new object[0];
+      }
+      if (obtained == childCount) {
+        return children;
+      }
+      object[] trimmed = new object[obtained];
+      System.Array.Copy(children, trimmed, obtained);
+      return trimmed;
+    }
+
+    private static bool NameEquals(
+        Accessibility.IAccessible container,
+        object childId,
+        string targetName) {
+      string name = Name(container, childId);
+      return string.Equals(
+        name, targetName, System.StringComparison.Ordinal);
+    }
+
+    private static void AddName(
+        Accessibility.IAccessible container,
+        object childId,
+        System.Collections.Generic.List<string> names) {
+      string name = Name(container, childId);
+      if (!string.IsNullOrWhiteSpace(name)) {
+        names.Add(name);
+      }
+    }
+
+    private static string Name(
+        Accessibility.IAccessible container, object childId) {
+      try {
+        return container.get_accName(childId);
+      } catch (System.Runtime.InteropServices.COMException) {
+        return null;
+      }
+    }
+  }
+
+  public static class NativeWindow {
+    private delegate bool EnumWindowsProc(
+      System.IntPtr window, System.IntPtr parameter);
+
+    [System.Runtime.InteropServices.DllImport("user32.dll")]
+    private static extern bool EnumWindows(
+      EnumWindowsProc callback, System.IntPtr parameter);
+
+    [System.Runtime.InteropServices.DllImport("user32.dll")]
+    private static extern bool EnumChildWindows(
+      System.IntPtr parent,
+      EnumWindowsProc callback,
+      System.IntPtr parameter);
+
+    [System.Runtime.InteropServices.DllImport("user32.dll")]
+    private static extern uint GetWindowThreadProcessId(
+      System.IntPtr window, out uint processId);
+
+    [System.Runtime.InteropServices.DllImport(
+      "user32.dll",
+      CharSet = System.Runtime.InteropServices.CharSet.Unicode)]
+    private static extern int GetClassName(
+      System.IntPtr window,
+      System.Text.StringBuilder className,
+      int maximumCount);
+
+    [System.Runtime.InteropServices.DllImport(
+      "user32.dll",
+      CharSet = System.Runtime.InteropServices.CharSet.Unicode,
+      SetLastError = true)]
+    public static extern System.IntPtr FindWindowEx(
+      System.IntPtr parent,
+      System.IntPtr childAfter,
+      string className,
+      string windowName);
+
+    public static System.IntPtr FindByProcessAndClass(
+        int processId, string targetClass) {
+      System.IntPtr result = System.IntPtr.Zero;
+      EnumWindows(delegate(System.IntPtr topLevel, System.IntPtr parameter) {
+        uint owner;
+        GetWindowThreadProcessId(topLevel, out owner);
+        if (owner != processId) {
+          return true;
+        }
+        if (ClassName(topLevel) == targetClass) {
+          result = topLevel;
+          return false;
+        }
+        EnumChildWindows(
+          topLevel,
+          delegate(System.IntPtr child, System.IntPtr childParameter) {
+            if (ClassName(child) == targetClass) {
+              result = child;
+              return false;
+            }
+            return true;
+          },
+          System.IntPtr.Zero);
+        return result == System.IntPtr.Zero;
+      }, System.IntPtr.Zero);
+      return result;
+    }
+
+    public static System.IntPtr FindMessageOnlyByProcessAndClass(
+        int processId, string targetClass) {
+      System.IntPtr messageWindow = new System.IntPtr(-3);
+      System.IntPtr child = System.IntPtr.Zero;
+      while (true) {
+        child = FindWindowEx(messageWindow, child, targetClass, null);
+        if (child == System.IntPtr.Zero) {
+          return System.IntPtr.Zero;
+        }
+        uint owner;
+        GetWindowThreadProcessId(child, out owner);
+        if (owner == processId) {
+          return child;
+        }
+      }
+    }
+
+    public static string DescribeProcessWindows(int processId) {
+      System.Collections.Generic.List<string> windows =
+        new System.Collections.Generic.List<string>();
+      EnumWindows(delegate(System.IntPtr topLevel, System.IntPtr parameter) {
+        uint owner;
+        GetWindowThreadProcessId(topLevel, out owner);
+        if (owner != processId) {
+          return true;
+        }
+        windows.Add(ClassName(topLevel));
+        EnumChildWindows(
+          topLevel,
+          delegate(System.IntPtr child, System.IntPtr childParameter) {
+            windows.Add(ClassName(child));
+            return true;
+          },
+          System.IntPtr.Zero);
+        return true;
+      }, System.IntPtr.Zero);
+      return string.Join(",", windows.ToArray());
+    }
+
+    private static string ClassName(System.IntPtr window) {
+      System.Text.StringBuilder className =
+        new System.Text.StringBuilder(256);
+      GetClassName(window, className, className.Capacity);
+      return className.ToString();
+    }
+  }
+}
+'@
+}
+
+function Write-Step {
+  param([string]$Message)
+  Write-Host ("[{0}] {1}" -f (Get-Date -Format "HH:mm:ss"), $Message)
+}
+
+function Wait-ServiceRunning {
+  param([string]$Name, [int]$TimeoutSeconds)
+  for ($i = 0; $i -lt $TimeoutSeconds; $i++) {
+    $service = Get-Service -Name $Name -ErrorAction SilentlyContinue
+    if ($service -and $service.Status -eq "Running") {
+      return
+    }
+    Start-Sleep -Seconds 1
+  }
+  throw "Service $Name did not reach Running state"
+}
+
+function Use-StagingService {
+  if (-not (Test-Path $InstalledDaemonPath)) {
+    throw "Installed daemon not found: $InstalledDaemonPath"
+  }
+  Write-Step "Reinstalling the installed service for staging"
+  Remove-Item $serviceDataDirectory -Recurse -Force -ErrorAction SilentlyContinue
+  Remove-Item $serviceLogDirectory -Recurse -Force -ErrorAction SilentlyContinue
+  & $InstalledDaemonPath install --environment staging `
+    --data-path $serviceDataDirectory `
+    --log-path $serviceLogDirectory `
+    --log-level debug
+  if ($LASTEXITCODE -ne 0) {
+    throw "lanternd staging install failed with exit code $LASTEXITCODE"
+  }
+  Wait-ServiceRunning -Name $ServiceName -TimeoutSeconds 60
+  Start-Sleep -Seconds 5
+
+  $service = Get-CimInstance Win32_Service -Filter "Name='$ServiceName'"
+  if ($service.PathName -notmatch '(?i)--environment\s+staging') {
+    throw "Installed service command does not persist --environment staging: $($service.PathName)"
+  }
+  if ($service.PathName -notmatch [regex]::Escape($serviceDataDirectory)) {
+    throw "Installed staging service is not using disposable data: $($service.PathName)"
+  }
+  $service | Select-Object Name, State, StartMode, PathName |
+    ConvertTo-Json | Set-Content (Join-Path $resolvedArtifacts "service.json")
+}
+
+function Wait-File {
+  param([string]$Path, [int]$TimeoutSeconds)
+  for ($i = 0; $i -lt $TimeoutSeconds; $i++) {
+    if (Test-Path $Path) { return }
+    Start-Sleep -Seconds 1
+  }
+  throw "Timed out waiting for $Path"
+}
+
+function Wait-ProcessMainWindow {
+  param([int]$ProcessID, [int]$TimeoutSeconds)
+  for ($i = 0; $i -lt $TimeoutSeconds; $i++) {
+    $process = Get-Process -Id $ProcessID -ErrorAction SilentlyContinue
+    if (-not $process) {
+      throw "Lantern process $ProcessID exited before creating a window"
+    }
+    $process.Refresh()
+    if ($process.MainWindowHandle -ne 0) {
+      return $process
+    }
+    Start-Sleep -Seconds 1
+  }
+  throw "Timed out waiting for Lantern main window"
+}
+
+function Wait-FlutterViewHandle {
+  param([int]$ProcessID, [int]$TimeoutSeconds)
+  for ($i = 0; $i -lt $TimeoutSeconds; $i++) {
+    $handle = [WindowsPaymentSmoke.NativeWindow]::FindByProcessAndClass(
+      $ProcessID,
+      "FLUTTERVIEW"
+    )
+    if ($handle -ne [IntPtr]::Zero) {
+      return $handle
+    }
+    Start-Sleep -Seconds 1
+  }
+  $messageOnly = [WindowsPaymentSmoke.NativeWindow]::FindMessageOnlyByProcessAndClass(
+    $ProcessID,
+    "FLUTTERVIEW"
+  )
+  $windows = [WindowsPaymentSmoke.NativeWindow]::DescribeProcessWindows(
+    $ProcessID
+  )
+  if ($messageOnly -ne [IntPtr]::Zero) {
+    throw "Lantern's FLUTTERVIEW remained message-only; windows=$windows"
+  }
+  throw "Lantern did not create a FLUTTERVIEW window; windows=$windows"
+}
+
+function Wait-AccessibleElement {
+  param(
+    [IntPtr]$ViewHandle,
+    [string]$AccessibleName,
+    [int]$TimeoutSeconds,
+    [string]$FailureLogPath,
+    [switch]$Optional
+  )
+  for ($i = 0; $i -lt $TimeoutSeconds; $i++) {
+    if ([WindowsPaymentSmoke.NativeAccessibility]::ContainsName(
+        $ViewHandle,
+        $AccessibleName
+      )) {
+      return $true
+    }
+    if ($FailureLogPath -and (Test-Path $FailureLogPath)) {
+      $failure = Select-String -Path $FailureLogPath `
+        -Pattern 'PAYMENT_CHECKOUT_SMOKE event=(rejected|bootstrap_error)' |
+        Select-Object -Last 1
+      if ($failure) {
+        throw "Lantern checkout bootstrap failed: $($failure.Line.Trim())"
+      }
+    }
+    Start-Sleep -Seconds 1
+  }
+  if ($Optional) { return $false }
+  $names = [WindowsPaymentSmoke.NativeAccessibility]::DescribeNames(
+    $ViewHandle
+  )
+  throw "Timed out waiting for accessible element '$AccessibleName'; names=$names"
+}
+
+function Invoke-AccessibleElement {
+  param(
+    [IntPtr]$ViewHandle,
+    [string]$AccessibleName
+  )
+  if (-not [WindowsPaymentSmoke.NativeAccessibility]::ClickByName(
+      $ViewHandle,
+      $AccessibleName
+    )) {
+    throw "Could not invoke accessible element '$AccessibleName'"
+  }
+}
+
+function Save-WindowScreenshot {
+  param(
+    [System.Windows.Automation.AutomationElement]$Root,
+    [string]$Path
+  )
+  $bounds = $Root.Current.BoundingRectangle
+  if ($bounds.Width -le 0 -or $bounds.Height -le 0) { return }
+  $bitmap = [System.Drawing.Bitmap]::new([int]$bounds.Width, [int]$bounds.Height)
+  $graphics = [System.Drawing.Graphics]::FromImage($bitmap)
+  try {
+    $graphics.CopyFromScreen(
+      [int]$bounds.X,
+      [int]$bounds.Y,
+      0,
+      0,
+      $bitmap.Size
+    )
+    $bitmap.Save($Path, [System.Drawing.Imaging.ImageFormat]::Png)
+  } finally {
+    $graphics.Dispose()
+    $bitmap.Dispose()
+  }
+}
+
+function Save-DesktopScreenshot {
+  param([string]$Path)
+  $bounds = [System.Windows.Forms.SystemInformation]::VirtualScreen
+  $bitmap = [System.Drawing.Bitmap]::new($bounds.Width, $bounds.Height)
+  $graphics = [System.Drawing.Graphics]::FromImage($bitmap)
+  try {
+    $graphics.CopyFromScreen(
+      $bounds.Left,
+      $bounds.Top,
+      0,
+      0,
+      $bitmap.Size
+    )
+    $bitmap.Save($Path, [System.Drawing.Imaging.ImageFormat]::Png)
+  } finally {
+    $graphics.Dispose()
+    $bitmap.Dispose()
+  }
+}
+
+function Copy-CaseLogs {
+  param([string]$Destination)
+  $appLogDirectory = Join-Path $env:PUBLIC "Lantern\logs"
+  if (Test-Path $appLogDirectory) {
+    Copy-Item $appLogDirectory (Join-Path $Destination "app-logs") -Recurse -Force
+  }
+  if (Test-Path $serviceLogDirectory) {
+    Copy-Item $serviceLogDirectory (Join-Path $Destination "daemon-logs") -Recurse -Force
+  }
+}
+
+function Wait-CheckoutDocument {
+  param(
+    [string]$LogPath,
+    [string]$HostPattern,
+    [int]$TimeoutSeconds,
+    [string]$ResultPath
+  )
+  $linePattern = 'PAYMENT_WEBVIEW_SMOKE event=load_stop host=(\S+) url=(\S+) document_length=(\d+)'
+  $lastLogText = ""
+  for ($i = 0; $i -lt $TimeoutSeconds; $i++) {
+    if (Test-Path $LogPath) {
+      $lastLogText = [string](
+        Get-Content $LogPath -Raw -ErrorAction SilentlyContinue
+      )
+      if ($lastLogText -match 'PAYMENT_CHECKOUT_SMOKE event=(rejected|bootstrap_error)') {
+        throw "Lantern could not prepare the requested checkout smoke"
+      }
+      foreach ($match in [regex]::Matches($lastLogText, $linePattern)) {
+        $hostName = $match.Groups[1].Value
+        $documentLength = [int]$match.Groups[3].Value
+        if ($hostName -match $HostPattern -and $documentLength -gt 0) {
+          if ($lastLogText -notmatch 'PAYMENT_WEBVIEW_SMOKE event=created') {
+            throw "The checkout page loaded without a WebView creation marker"
+          }
+          @{
+            host = $hostName
+            url = $match.Groups[2].Value
+            documentLength = $documentLength
+          } | ConvertTo-Json | Set-Content $ResultPath
+          return
+        }
+      }
+    }
+    Start-Sleep -Seconds 1
+  }
+  if ($lastLogText -match 'PAYMENT_WEBVIEW_SMOKE event=navigation_error') {
+    throw "The checkout WebView reported a main-frame navigation error"
+  }
+  if ($lastLogText -match 'PAYMENT_WEBVIEW_SMOKE event=document_error') {
+    throw "The checkout WebView could not inspect the loaded document"
+  }
+  throw "No non-empty checkout document loaded from expected host pattern $HostPattern"
+}
+
+function Wait-LauncherResult {
+  param(
+    [string]$Path,
+    [System.Diagnostics.Process]$Process,
+    [int]$TimeoutSeconds,
+    [string]$ErrorPath
+  )
+  for ($i = 0; $i -lt $TimeoutSeconds; $i++) {
+    if (Test-Path $Path) { return }
+    $Process.Refresh()
+    if ($Process.HasExited) {
+      Start-Sleep -Seconds 1
+      if (Test-Path $Path) { return }
+      $errorDetails = if ($ErrorPath -and (Test-Path $ErrorPath)) {
+        (Get-Content $ErrorPath -Raw -ErrorAction SilentlyContinue).Trim()
+      } else {
+        ""
+      }
+      if ($errorDetails) {
+        throw "Smoke-user launcher exited with code $($Process.ExitCode): $errorDetails"
+      }
+      throw "Smoke-user launcher exited with code $($Process.ExitCode) without writing a result"
+    }
+    Start-Sleep -Seconds 1
+  }
+  throw "Timed out waiting for the smoke-user launcher"
+}
+
+function Invoke-SmokeUserCheckout {
+  param(
+    [string]$AppPath,
+    [string]$CheckoutProvider,
+    [string]$CheckoutRunID,
+    [string]$ProcessDiagnosticsPath,
+    [string]$WebViewUDFPath,
+    [string]$UserProfilePath,
+    [string]$ResultPath,
+    [string]$AppLogPath,
+    [string]$ExpectedHostPattern,
+    [string]$WebViewPath,
+    [string]$CheckoutImagePath,
+    [string]$FinalImagePath,
+    [string]$TranscriptPath,
+    [int]$TimeoutSeconds
+  )
+
+  $app = $null
+  $root = $null
+  $transcriptStarted = $false
+  try {
+    $env:USERPROFILE = $UserProfilePath
+    $env:LOCALAPPDATA = Join-Path $UserProfilePath "AppData\Local"
+    $env:APPDATA = Join-Path $UserProfilePath "AppData\Roaming"
+    $env:HOMEDRIVE = Split-Path -Qualifier $UserProfilePath
+    $env:HOMEPATH = $UserProfilePath.Substring($env:HOMEDRIVE.Length)
+    $env:TEMP = Join-Path $env:LOCALAPPDATA "Temp"
+    $env:TMP = $env:TEMP
+    New-Item -ItemType Directory -Path $env:TEMP -Force | Out-Null
+    Start-Transcript -Path $TranscriptPath -Force | Out-Null
+    $transcriptStarted = $true
+    $null = Initialize-NativeSmokeHelpers
+    [Environment]::SetEnvironmentVariable(
+      "WEBVIEW2_USER_DATA_FOLDER",
+      $null,
+      [EnvironmentVariableTarget]::Process
+    )
+
+    $identity = [Security.Principal.WindowsIdentity]::GetCurrent()
+    $principal = [Security.Principal.WindowsPrincipal]::new($identity)
+    $isAdmin = $principal.IsInRole(
+      [Security.Principal.WindowsBuiltInRole]::Administrator
+    )
+    $installWritePath = Join-Path (Split-Path $AppPath -Parent) (
+      "smoke-write-" + [Guid]::NewGuid().ToString("N")
+    )
+    $canWriteInstallDirectory = $false
+    try {
+      New-Item -ItemType File -Path $installWritePath -Force `
+        -ErrorAction Stop | Out-Null
+      $canWriteInstallDirectory = $true
+    } catch {
+    } finally {
+      Remove-Item $installWritePath -Force -ErrorAction SilentlyContinue
+    }
+
+    $localAppData = $env:LOCALAPPDATA
+    $externalUDF = [Environment]::GetEnvironmentVariable(
+      "WEBVIEW2_USER_DATA_FOLDER",
+      "Process"
+    )
+    $app = Start-Process -FilePath $AppPath -ArgumentList @(
+      "--payment-checkout-smoke=$CheckoutProvider",
+      "--payment-checkout-run-id=$CheckoutRunID"
+    ) -PassThru
+    @{
+      processId = $app.Id
+      username = $identity.Name
+      isAdmin = $isAdmin
+      canWriteInstallDirectory = $canWriteInstallDirectory
+      externalWebView2UserDataFolder = $externalUDF
+      localAppData = $localAppData
+      profilePath = $UserProfilePath
+    } | ConvertTo-Json | Set-Content $ProcessDiagnosticsPath
+
+    $app = Wait-ProcessMainWindow -ProcessID $app.Id -TimeoutSeconds 90
+    $flutterViewHandle = Wait-FlutterViewHandle `
+      -ProcessID $app.Id -TimeoutSeconds 30
+    $processIsElevated = [WindowsPaymentSmoke.NativeToken]::IsElevated($app.Id)
+    $diagnostics = Get-Content $ProcessDiagnosticsPath -Raw | ConvertFrom-Json
+    $diagnostics | Add-Member -NotePropertyName processIsElevated `
+      -NotePropertyValue $processIsElevated
+    $diagnostics | Add-Member -NotePropertyName mainWindowHandle `
+      -NotePropertyValue ([IntPtr]$app.MainWindowHandle).ToInt64()
+    $diagnostics | Add-Member -NotePropertyName flutterViewHandle `
+      -NotePropertyValue $flutterViewHandle.ToInt64()
+    $diagnostics | ConvertTo-Json | Set-Content $ProcessDiagnosticsPath
+    if ($isAdmin -or $processIsElevated) {
+      throw "The installed Lantern process has an elevated access token"
+    }
+    if ($canWriteInstallDirectory) {
+      throw "The smoke user can write beside the installed executable"
+    }
+    if (-not [string]::IsNullOrWhiteSpace($externalUDF)) {
+      throw "Primary smoke inherited WEBVIEW2_USER_DATA_FOLDER=$externalUDF"
+    }
+
+    Write-Step "Attached accessibility automation to Lantern's FLUTTERVIEW child window"
+    $root = [System.Windows.Automation.AutomationElement]::FromHandle(
+      $flutterViewHandle
+    )
+    $providerTitle = (Get-Culture).TextInfo.ToTitleCase($CheckoutProvider)
+    $providerName = "$providerTitle payment method"
+    $checkoutName = "Continue with $providerTitle"
+    $null = Wait-AccessibleElement -ViewHandle $flutterViewHandle `
+      -AccessibleName $providerName -TimeoutSeconds 90 `
+      -FailureLogPath $AppLogPath
+    $checkoutVisible = Wait-AccessibleElement -ViewHandle $flutterViewHandle `
+      -AccessibleName $checkoutName `
+      -TimeoutSeconds 2 -Optional
+    if (-not $checkoutVisible) {
+      Invoke-AccessibleElement -ViewHandle $flutterViewHandle `
+        -AccessibleName $providerName
+      $null = Wait-AccessibleElement -ViewHandle $flutterViewHandle `
+        -AccessibleName $checkoutName `
+        -TimeoutSeconds 20 -FailureLogPath $AppLogPath
+    }
+    Invoke-AccessibleElement -ViewHandle $flutterViewHandle `
+      -AccessibleName $checkoutName
+
+    Wait-CheckoutDocument -LogPath $AppLogPath `
+      -HostPattern $ExpectedHostPattern -TimeoutSeconds $TimeoutSeconds `
+      -ResultPath $WebViewPath
+
+    $udfPath = Join-Path $localAppData "Lantern\WebView2"
+    for ($i = 0; $i -lt 30; $i++) {
+      if (Test-Path $udfPath) { break }
+      if ($app.HasExited) { break }
+      Start-Sleep -Seconds 1
+      $app.Refresh()
+    }
+    $udfWritable = $false
+    $udfProbe = Join-Path $udfPath (
+      "write-probe-" + [Guid]::NewGuid().ToString("N")
+    )
+    try {
+      New-Item -ItemType File -Path $udfProbe -Force `
+        -ErrorAction Stop | Out-Null
+      $udfWritable = $true
+    } catch {
+    } finally {
+      Remove-Item $udfProbe -Force -ErrorAction SilentlyContinue
+    }
+    @{
+      path = $udfPath
+      exists = (Test-Path $udfPath)
+      writable = $udfWritable
+    } | ConvertTo-Json | Set-Content $WebViewUDFPath
+
+    Save-WindowScreenshot -Root $root -Path $CheckoutImagePath
+    Save-WindowScreenshot -Root $root -Path $FinalImagePath
+    @{
+      success = $true
+      processId = $app.Id
+      provider = $CheckoutProvider
+    } | ConvertTo-Json | Set-Content $ResultPath
+
+    $app.WaitForExit()
+  } catch {
+    $failure = $_
+    try {
+      if ($root) {
+        Save-WindowScreenshot -Root $root -Path $FinalImagePath
+      } else {
+        Save-DesktopScreenshot -Path $FinalImagePath
+      }
+    } catch {
+      Write-Warning "Could not capture smoke-user screenshot: $_"
+    }
+    @{
+      success = $false
+      error = $failure.Exception.Message
+      provider = $CheckoutProvider
+    } | ConvertTo-Json | Set-Content $ResultPath
+    throw $failure
+  } finally {
+    if ($transcriptStarted) {
+      try {
+        Stop-Transcript | Out-Null
+      } catch {
+      }
+    }
+  }
+}
+
+function Remove-SmokeAccount {
+  param([string]$Username, [string]$SID)
+  if (Get-LocalUser -Name $Username -ErrorAction SilentlyContinue) {
+    Remove-LocalUser -Name $Username
+  }
+  if ([string]::IsNullOrWhiteSpace($SID)) { return }
+  for ($i = 0; $i -lt 15; $i++) {
+    $profile = Get-CimInstance Win32_UserProfile -Filter "SID='$SID'" -ErrorAction SilentlyContinue
+    if (-not $profile) { return }
+    if (-not $profile.Loaded) {
+      Remove-CimInstance $profile
+      return
+    }
+    Start-Sleep -Seconds 1
+  }
+  Write-Warning "Disposable profile $SID remained loaded and could not be removed"
+}
+
+function Invoke-CheckoutCase {
+  param([string]$Provider, [string]$HostPattern, [string]$RunID)
+
+  $caseDirectory = Join-Path $resolvedArtifacts $Provider
+  New-Item -ItemType Directory -Path $caseDirectory -Force | Out-Null
+  @{
+    provider = $Provider
+    runId = $RunID
+    githubRunId = $env:GITHUB_RUN_ID
+    githubRunAttempt = $env:GITHUB_RUN_ATTEMPT
+  } | ConvertTo-Json | Set-Content (Join-Path $caseDirectory "run.json")
+  $transcript = Join-Path $caseDirectory "orchestration.log"
+  $username = "lntsmk" + ([Guid]::NewGuid().ToString("N").Substring(0, 10))
+  $sid = $null
+  $credential = $null
+  $launcherProcess = $null
+  $appProcess = $null
+  $sharedAppDirectory = $null
+  $diagnosticsPath = $null
+  $udfCheckPath = $null
+  $automationResultPath = $null
+  $childWebViewPath = $null
+  $childCheckoutImagePath = $null
+  $childFinalImagePath = $null
+  $launcherLogPath = $null
+  $launcherStdoutPath = $null
+  $launcherStderrPath = $null
+  $launcherConfigPath = $null
+  $profilePath = $null
+  $transcriptStarted = $false
+  $priorUDF = [Environment]::GetEnvironmentVariable(
+    "WEBVIEW2_USER_DATA_FOLDER",
+    [EnvironmentVariableTarget]::Process
+  )
+
+  try {
+    Start-Transcript -Path $transcript -Force | Out-Null
+    $transcriptStarted = $true
+    $passwordText = "L@ntern!" + ([Guid]::NewGuid().ToString("N"))
+    $securePassword = ConvertTo-SecureString $passwordText -AsPlainText -Force
+    $credential = [System.Management.Automation.PSCredential]::new(
+      ".\$username",
+      $securePassword
+    )
+    $user = New-LocalUser -Name $username -Password $securePassword `
+      -AccountNeverExpires -PasswordNeverExpires
+    $sid = $user.SID.Value
+    # The daemon accepts members of Administrators. UAC still gives the app a
+    # filtered, non-elevated token, which the checks below verify.
+    $administrators = Get-LocalGroup -SID "S-1-5-32-544"
+    Add-LocalGroupMember -Group $administrators -Member $user
+    $administratorsMember = Get-LocalGroupMember -Group $administrators |
+      Where-Object { $_.SID.Value -eq $sid }
+    if (-not $administratorsMember) {
+      throw "Could not grant the smoke user access to the installed Lantern service"
+    }
+
+    # Create the profile before the real launch so the child process does not
+    # inherit the runner account's AppData paths.
+    $profileBootstrap = Start-Process -FilePath "powershell.exe" `
+      -Credential $credential -LoadUserProfile -Wait -PassThru `
+      -ArgumentList @("-NoLogo", "-NoProfile", "-NonInteractive", "-Command", "exit 0")
+    if ($profileBootstrap.ExitCode -ne 0) {
+      throw "Could not initialize the disposable user profile"
+    }
+    $profile = $null
+    for ($i = 0; $i -lt 15; $i++) {
+      $profile = Get-CimInstance Win32_UserProfile -Filter "SID='$sid'" `
+        -ErrorAction SilentlyContinue
+      if ($profile -and -not [string]::IsNullOrWhiteSpace($profile.LocalPath)) {
+        break
+      }
+      Start-Sleep -Seconds 1
+    }
+    if (-not $profile -or [string]::IsNullOrWhiteSpace($profile.LocalPath)) {
+      throw "Windows did not create a profile for disposable user $username"
+    }
+    $profilePath = [Environment]::ExpandEnvironmentVariables($profile.LocalPath)
+
+    Write-Step "Starting $Provider checkout as disposable non-elevated user $username"
+    [Environment]::SetEnvironmentVariable(
+      "WEBVIEW2_USER_DATA_FOLDER",
+      $null,
+      [EnvironmentVariableTarget]::Process
+    )
+
+    $sharedAppDirectory = Join-Path $env:PUBLIC "Lantern"
+    New-Item -ItemType Directory -Path $sharedAppDirectory -Force | Out-Null
+    & icacls.exe $sharedAppDirectory /grant "*$sid`:(OI)(CI)M" /T /C | Out-Null
+    if ($LASTEXITCODE -ne 0) {
+      throw "Could not grant the smoke user access to $sharedAppDirectory"
+    }
+
+    $exchangeDirectory = Join-Path $sharedAppDirectory "payment-smoke\$RunID-$Provider"
+    New-Item -ItemType Directory -Path $exchangeDirectory -Force | Out-Null
+    Remove-Item (Join-Path $sharedAppDirectory "data") -Recurse -Force -ErrorAction SilentlyContinue
+    Remove-Item (Join-Path $sharedAppDirectory "logs") -Recurse -Force -ErrorAction SilentlyContinue
+
+    $diagnosticsPath = Join-Path $exchangeDirectory "process.json"
+    $udfCheckPath = Join-Path $exchangeDirectory "udf.json"
+    $automationResultPath = Join-Path $exchangeDirectory "automation-result.json"
+    $childWebViewPath = Join-Path $exchangeDirectory "webview.json"
+    $childCheckoutImagePath = Join-Path $exchangeDirectory "checkout.png"
+    $childFinalImagePath = Join-Path $exchangeDirectory "final.png"
+    $launcherLogPath = Join-Path $exchangeDirectory "automation.log"
+    $launcherStdoutPath = Join-Path $exchangeDirectory "launcher-stdout.log"
+    $launcherStderrPath = Join-Path $exchangeDirectory "launcher-stderr.log"
+    $launcherPath = Join-Path $exchangeDirectory "launch.ps1"
+    $launcherConfigPath = Join-Path $exchangeDirectory "launcher.json"
+    $flutterLog = Join-Path $env:PUBLIC "Lantern\logs\flutter.log"
+    # Run UI Automation in the same logon session as Flutter. Cross-user
+    # automation can see the native host window but not Flutter's semantics.
+    Copy-Item $PSCommandPath $launcherPath -Force
+    @{
+      appPath = $InstalledAppPath
+      provider = $Provider
+      runId = $RunID
+      diagnosticsPath = $diagnosticsPath
+      udfCheckPath = $udfCheckPath
+      profilePath = $profilePath
+      automationResultPath = $automationResultPath
+      flutterLogPath = $flutterLog
+      hostPattern = $HostPattern
+      webViewResultPath = $childWebViewPath
+      checkoutScreenshotPath = $childCheckoutImagePath
+      finalScreenshotPath = $childFinalImagePath
+      launcherLogPath = $launcherLogPath
+      waitSeconds = $WaitSeconds
+    } | ConvertTo-Json | Set-Content $launcherConfigPath
+
+    $launcherArguments = @(
+      "-NoLogo",
+      "-NoProfile",
+      "-ExecutionPolicy", "Bypass",
+      "-File", "`"$launcherPath`"",
+      "-Mode", "launcher",
+      "-LauncherConfigPath", "`"$launcherConfigPath`""
+    )
+    $launcherCommandLine = $launcherArguments -join " "
+    if ($launcherCommandLine.Length -gt 900) {
+      throw "Smoke-user launcher command line is too long"
+    }
+    $launcherProcess = Start-Process -FilePath "powershell.exe" `
+      -Credential $credential -LoadUserProfile `
+      -ArgumentList $launcherArguments `
+      -RedirectStandardOutput $launcherStdoutPath `
+      -RedirectStandardError $launcherStderrPath -PassThru
+
+    Wait-LauncherResult -Path $automationResultPath -Process $launcherProcess `
+      -TimeoutSeconds ($WaitSeconds + 150) -ErrorPath $launcherStderrPath
+    $automationResult = Get-Content $automationResultPath -Raw |
+      ConvertFrom-Json
+    if (-not $automationResult.success) {
+      throw "Smoke-user checkout failed: $($automationResult.error)"
+    }
+
+    $diagnostics = Get-Content $diagnosticsPath -Raw | ConvertFrom-Json
+    if ($diagnostics.isAdmin) {
+      throw "The installed app was launched with an administrator token"
+    }
+    if ($diagnostics.canWriteInstallDirectory) {
+      throw "The smoke user can write beside the installed executable"
+    }
+    if (-not [string]::IsNullOrWhiteSpace($diagnostics.externalWebView2UserDataFolder)) {
+      throw "Primary smoke inherited WEBVIEW2_USER_DATA_FOLDER=$($diagnostics.externalWebView2UserDataFolder)"
+    }
+    $expectedLocalAppData = Join-Path $profilePath "AppData\Local"
+    if ($diagnostics.localAppData -ne $expectedLocalAppData) {
+      throw "Lantern inherited the wrong LOCALAPPDATA: $($diagnostics.localAppData)"
+    }
+    $diagnostics | ConvertTo-Json | Set-Content (Join-Path $caseDirectory "process.json")
+    if ($diagnostics.processIsElevated) {
+      throw "The installed Lantern process has an elevated access token"
+    }
+    $appProcess = Get-Process -Id $diagnostics.processId -ErrorAction Stop
+
+    Wait-File -Path $udfCheckPath -TimeoutSeconds 30
+    $udf = Get-Content $udfCheckPath -Raw | ConvertFrom-Json
+    Copy-Item $udfCheckPath (Join-Path $caseDirectory "webview2-udf.json") -Force
+    $expectedUDF = Join-Path $diagnostics.localAppData "Lantern\WebView2"
+    if (-not $udf.exists -or -not $udf.writable -or $udf.path -ne $expectedUDF) {
+      throw "Unexpected or unwritable WebView2 folder: $($udf | ConvertTo-Json -Compress)"
+    }
+    $escapedExpectedUDF = [regex]::Escape($expectedUDF)
+    $flutterLogText = Get-Content $flutterLog -Raw
+    if ($flutterLogText -notmatch "WEBVIEW2_DIAGNOSTIC user_data_folder=$escapedExpectedUDF") {
+      throw "Flutter did not record the actual per-user WebView2 folder $expectedUDF"
+    }
+
+    Write-Step "$Provider checkout rendered successfully"
+  } finally {
+    if ($appProcess) {
+      Stop-Process -Id $appProcess.Id -Force -ErrorAction SilentlyContinue
+    } elseif ($diagnosticsPath -and (Test-Path $diagnosticsPath)) {
+      try {
+        $startedProcessID = (Get-Content $diagnosticsPath -Raw | ConvertFrom-Json).processId
+        Stop-Process -Id $startedProcessID -Force -ErrorAction SilentlyContinue
+      } catch {
+      }
+    }
+    if ($launcherProcess) {
+      $launcherProcess.Refresh()
+      if (-not $launcherProcess.HasExited -and
+          -not $launcherProcess.WaitForExit(5000)) {
+        Stop-Process -Id $launcherProcess.Id -Force -ErrorAction SilentlyContinue
+      }
+    }
+    Start-Sleep -Seconds 1
+    $childArtifacts = @(
+      [pscustomobject]@{
+        Source = $launcherLogPath
+        Destination = Join-Path $caseDirectory "automation.log"
+      },
+      [pscustomobject]@{
+        Source = $launcherStdoutPath
+        Destination = Join-Path $caseDirectory "launcher-stdout.log"
+      },
+      [pscustomobject]@{
+        Source = $launcherStderrPath
+        Destination = Join-Path $caseDirectory "launcher-stderr.log"
+      },
+      [pscustomobject]@{
+        Source = $childWebViewPath
+        Destination = Join-Path $caseDirectory "webview.json"
+      },
+      [pscustomobject]@{
+        Source = $childCheckoutImagePath
+        Destination = Join-Path $caseDirectory "checkout.png"
+      },
+      [pscustomobject]@{
+        Source = $childFinalImagePath
+        Destination = Join-Path $caseDirectory "final.png"
+      }
+    )
+    foreach ($artifact in $childArtifacts) {
+      if ($artifact.Source -and (Test-Path $artifact.Source)) {
+        try {
+          Copy-Item $artifact.Source $artifact.Destination -Force
+        } catch {
+          Write-Warning "Could not collect $($artifact.Source): $_"
+        }
+      }
+    }
+    try {
+      if (-not (Test-Path (Join-Path $caseDirectory "final.png"))) {
+        Save-DesktopScreenshot -Path (Join-Path $caseDirectory "final.png")
+      }
+    } catch {
+      Write-Warning "Could not capture final screenshot: $_"
+    }
+    if ($udfCheckPath -and (Test-Path $udfCheckPath)) {
+      Copy-Item $udfCheckPath (Join-Path $caseDirectory "webview2-udf.json") -Force
+    }
+    if ($diagnosticsPath -and (Test-Path $diagnosticsPath) -and
+        -not (Test-Path (Join-Path $caseDirectory "process.json"))) {
+      Copy-Item $diagnosticsPath (Join-Path $caseDirectory "process.json") -Force
+    }
+    $finalFlutterLog = Join-Path $env:PUBLIC "Lantern\logs\flutter.log"
+    if (Test-Path $finalFlutterLog) {
+      Select-String -Path $finalFlutterLog `
+        -Pattern 'PAYMENT_WEBVIEW_SMOKE|WEBVIEW2_DIAGNOSTIC|PAYMENT_CHECKOUT_SMOKE' |
+        ForEach-Object { $_.Line } |
+        Set-Content (Join-Path $caseDirectory "webview-events.log")
+    }
+    try {
+      Copy-CaseLogs -Destination $caseDirectory
+    } catch {
+      Write-Warning "Could not collect payment smoke logs: $_"
+    }
+    if ($sid -and $sharedAppDirectory -and (Test-Path $sharedAppDirectory)) {
+      & icacls.exe $sharedAppDirectory /remove "*$sid" /T /C | Out-Null
+    }
+    [Environment]::SetEnvironmentVariable(
+      "WEBVIEW2_USER_DATA_FOLDER",
+      $priorUDF,
+      [EnvironmentVariableTarget]::Process
+    )
+    if ($sid -or (Get-LocalUser -Name $username -ErrorAction SilentlyContinue)) {
+      try {
+        Remove-SmokeAccount -Username $username -SID $sid
+      } catch {
+        Write-Warning "Could not fully remove disposable smoke account: $_"
+      }
+    }
+    if ($transcriptStarted) {
+      try {
+        Stop-Transcript | Out-Null
+      } catch {
+      }
+    }
+  }
+}
+
+if ($Mode -eq "launcher") {
+  if (-not $LauncherConfigPath -or -not (Test-Path $LauncherConfigPath)) {
+    throw "Smoke-user launcher config not found: $LauncherConfigPath"
+  }
+  $launcherConfig = Get-Content $LauncherConfigPath -Raw | ConvertFrom-Json
+  Invoke-SmokeUserCheckout `
+    -AppPath $launcherConfig.appPath `
+    -CheckoutProvider $launcherConfig.provider `
+    -CheckoutRunID $launcherConfig.runId `
+    -ProcessDiagnosticsPath $launcherConfig.diagnosticsPath `
+    -WebViewUDFPath $launcherConfig.udfCheckPath `
+    -UserProfilePath $launcherConfig.profilePath `
+    -ResultPath $launcherConfig.automationResultPath `
+    -AppLogPath $launcherConfig.flutterLogPath `
+    -ExpectedHostPattern $launcherConfig.hostPattern `
+    -WebViewPath $launcherConfig.webViewResultPath `
+    -CheckoutImagePath $launcherConfig.checkoutScreenshotPath `
+    -FinalImagePath $launcherConfig.finalScreenshotPath `
+    -TranscriptPath $launcherConfig.launcherLogPath `
+    -TimeoutSeconds $launcherConfig.waitSeconds
+  return
+}
+
+if (-not (Test-Path $InstalledAppPath)) {
+  throw "Installed Lantern executable not found: $InstalledAppPath"
+}
+
+Use-StagingService
+Invoke-CheckoutCase -Provider "stripe" -HostPattern '^checkout\.stripe\.com$' `
+  -RunID ([Guid]::NewGuid().ToString())
+Invoke-CheckoutCase -Provider "shepherd" -HostPattern $ShepherdHostPattern `
+  -RunID ([Guid]::NewGuid().ToString())
diff --git a/.github/scripts/windows_smoke_suite.ps1 b/.github/scripts/windows_smoke_suite.ps1
index d16e0508bd..752fc366bf 100644
--- a/.github/scripts/windows_smoke_suite.ps1
+++ b/.github/scripts/windows_smoke_suite.ps1
@@ -16,6 +16,8 @@ param(
   [switch]$ForceFullTunnel,
   [switch]$RunSplitTunnelWebsiteSmoke,
   [switch]$RunConfigUrlSmoke,
+  [switch]$RunPaymentCheckoutSmoke,
+  [string]$PaymentSmokeArtifactDirectory = "build/windows-payment-checkout-smoke",
   [switch]$UseInstaller
 )
 
@@ -365,6 +367,21 @@ try {
         -ForceFullTunnel:$ForceFullTunnel
     }
   }
+
+  if ($RunPaymentCheckoutSmoke) {
+    if (-not $UseInstaller) {
+      throw "The payment checkout smoke requires the generated installer"
+    }
+    Write-Step "Running installed Windows payment checkout smoke tests"
+    & "$PSScriptRoot/windows_payment_checkout_smoke.ps1" `
+      -ServiceName $ServiceName `
+      -ArtifactDirectory $PaymentSmokeArtifactDirectory
+    if ($LASTEXITCODE -ne 0) {
+      throw "Windows payment checkout smoke failed with exit code $LASTEXITCODE"
+    }
+  } else {
+    Write-Step "Skipping installed Windows payment checkout smoke tests."
+  }
 }
 finally {
   try {
diff --git a/.github/workflows/app-smoke-tests.yml b/.github/workflows/app-smoke-tests.yml
index 67b341d86d..26c8d18f8c 100644
--- a/.github/workflows/app-smoke-tests.yml
+++ b/.github/workflows/app-smoke-tests.yml
@@ -27,6 +27,11 @@ on:
         required: false
         type: boolean
         default: true
+      windows_payment_checkout_smoke:
+        description: "Render staging Stripe and Shepherd checkout in the installed Windows app"
+        required: false
+        type: boolean
+        default: true
       macos_connect_smoke:
         description: "Include macOS connect/disconnect smoke when platforms=all (requires self-hosted runner with approved system extension)"
         required: false
@@ -145,6 +150,7 @@ jobs:
       skip_signing: true
       enable_ip_check: ${{ inputs.enable_ip_check }}
       run_connect_smoke: ${{ inputs.windows_connect_smoke }}
+      run_payment_checkout_smoke: ${{ inputs.windows_payment_checkout_smoke }}
       run_split_tunnel_website_smoke: ${{ inputs.windows_split_tunnel_website_smoke }}
       run_config_url_smoke: false
       force_full_tunnel_smoke: ${{ inputs.force_full_tunnel_smoke }}
diff --git a/.github/workflows/build-windows.yml b/.github/workflows/build-windows.yml
index d2f5be017a..4af7af5031 100644
--- a/.github/workflows/build-windows.yml
+++ b/.github/workflows/build-windows.yml
@@ -34,6 +34,11 @@ on:
         required: false
         type: boolean
         default: true
+      run_payment_checkout_smoke:
+        description: "Run installed-app staging payment checkout smoke tests"
+        required: false
+        type: boolean
+        default: false
       run_split_tunnel_website_smoke:
         description: "Run website split tunneling smoke test"
         required: false
@@ -302,16 +307,27 @@ jobs:
           $forceFullTunnelSmoke = "${{ inputs.force_full_tunnel_smoke }}" -eq "true"
           $enableIpCheck = "${{ inputs.enable_ip_check }}" -eq "true"
           $runConnectSmoke = "${{ inputs.run_connect_smoke }}" -eq "true"
-          Write-Host "Windows smoke options: connect=$runConnectSmoke splitTunnelWebsite=$runSplitTunnelWebsiteSmoke configUrl=$runConfigUrlSmoke forceFullTunnel=$forceFullTunnelSmoke ipCheck=$enableIpCheck"
+          $runPaymentCheckoutSmoke = "${{ inputs.run_payment_checkout_smoke }}" -eq "true"
+          Write-Host "Windows smoke options: connect=$runConnectSmoke paymentCheckout=$runPaymentCheckoutSmoke splitTunnelWebsite=$runSplitTunnelWebsiteSmoke configUrl=$runConfigUrlSmoke forceFullTunnel=$forceFullTunnelSmoke ipCheck=$enableIpCheck"
           ./.github/scripts/windows_smoke_suite.ps1 `
             -UseInstaller `
             -InstallerPath $installerPath `
             -RunConnectSmoke:$runConnectSmoke `
+            -RunPaymentCheckoutSmoke:$runPaymentCheckoutSmoke `
             -RunSplitTunnelWebsiteSmoke:$runSplitTunnelWebsiteSmoke `
             -RunConfigUrlSmoke:$runConfigUrlSmoke `
             -EnableIpCheck:$enableIpCheck `
             -ForceFullTunnel:$forceFullTunnelSmoke
 
+      - name: Upload Windows payment checkout smoke artifacts
+        if: ${{ always() && inputs.run_payment_checkout_smoke }}
+        uses: actions/upload-artifact@v4
+        with:
+          name: windows-payment-checkout-smoke
+          path: build/windows-payment-checkout-smoke
+          if-no-files-found: warn
+          retention-days: 7
+
       # Transitional fallback kept in place while the auth + connect smoke suite stabilizes.
       - name: Windows UI auth smoke integration
         if: ${{ inputs.run_auth_smoke }}
diff --git a/go.mod b/go.mod
index 23c1bcfdc5..c170b2dff6 100644
--- a/go.mod
+++ b/go.mod
@@ -25,7 +25,7 @@ replace github.com/quic-go/qpack => github.com/quic-go/qpack v0.5.1
 require (
 	github.com/alecthomas/assert/v2 v2.3.0
 	github.com/getlantern/lantern-server-provisioner v0.0.0-20251031121934-8ea031fccfa9
-	github.com/getlantern/radiance v0.0.0-20260730161730-76fcac0ceebb
+	github.com/getlantern/radiance v0.0.0-20260724161730-2ef18c71ad81
 	github.com/sagernet/sing-box v1.12.22
 	golang.org/x/mobile v0.0.0-20250711185624-d5bb5ecc55c0
 	golang.org/x/sys v0.45.0
diff --git a/go.sum b/go.sum
index 2b709c573a..d6491c20d7 100644
--- a/go.sum
+++ b/go.sum
@@ -259,8 +259,8 @@ github.com/getlantern/pluriconfig v0.0.0-20251126214241-8cc8bc561535 h1:rtDmW8YL
 github.com/getlantern/pluriconfig v0.0.0-20251126214241-8cc8bc561535/go.mod h1:WKJEdjMOD4IuTRYwjQHjT4bmqDl5J82RShMLxPAvi0Q=
 github.com/getlantern/publicip v0.0.0-20260328175246-2c460fe80c6b h1:gMYJzEhLrmIqQ+JnjiYNm+UyUDalK3WUmVyecFwmV5g=
 github.com/getlantern/publicip v0.0.0-20260328175246-2c460fe80c6b/go.mod h1:NpfXdK4ldEKkjQ4P1R+DBF4ua5VFOlxmgHROTnYrApg=
-github.com/getlantern/radiance v0.0.0-20260730161730-76fcac0ceebb h1:1VhnolDkNBFI7LmG6IAHgabJKrR7/B8LOYLFEne5wuo=
-github.com/getlantern/radiance v0.0.0-20260730161730-76fcac0ceebb/go.mod h1:BUKzQxV+sKuRySBLPTVHDt1XkPqoIdx/G+pB9euO4LQ=
+github.com/getlantern/radiance v0.0.0-20260724161730-2ef18c71ad81 h1:goJj8l9quR8bi4A4UGewR0l+euUSUAuEnFEKmLMYtE4=
+github.com/getlantern/radiance v0.0.0-20260724161730-2ef18c71ad81/go.mod h1:3ioylshJuvd1dJEUydJvIWjSXllphapzDk8HQgiyPnc=
 github.com/getlantern/samizdat v0.0.3-0.20260724223841-a5ee9ab56830 h1:RZd3CELOtQUEzIE5kPdEO9HYg+7JYbR3OTdC+3P/wng=
 github.com/getlantern/samizdat v0.0.3-0.20260724223841-a5ee9ab56830/go.mod h1:uEeykQSW2/6rTjfPlj3MTTo59poSHXfAHTGgzYDkbr0=
 github.com/getlantern/semconv v0.0.0-20260327040646-21845dda05cb h1:c5YM7b3a4r2J8Eh89KkI6M/iTFe6Bi+b8AJlfkKdFq4=
diff --git a/ios/Tunnel/SingBox/ExtensionProvider.swift b/ios/Tunnel/SingBox/ExtensionProvider.swift
index 88d6f1bda1..4be6cdb22d 100644
--- a/ios/Tunnel/SingBox/ExtensionProvider.swift
+++ b/ios/Tunnel/SingBox/ExtensionProvider.swift
@@ -110,7 +110,7 @@ class ExtensionProvider: NEPacketTunnelProvider {
     opts.dataDir = FilePath.dataDirectory.relativePath
     opts.logDir = FilePath.logsDirectory.relativePath
     // Intentionally left empty. The app and extension don't share a keychain access
-    // Radiance resolves the device ID from the main app process. 
+    // Radiance resolves the device ID from the main app process.
     opts.deviceid = ""
     opts.logLevel = "trace"
     opts.locale = Locale.current.identifier
diff --git a/lib/core/smoke/payment_checkout_smoke.dart b/lib/core/smoke/payment_checkout_smoke.dart
new file mode 100644
index 0000000000..f2b14a20cf
--- /dev/null
+++ b/lib/core/smoke/payment_checkout_smoke.dart
@@ -0,0 +1,67 @@
+/// Command-line settings for the Windows checkout smoke.
+class PaymentCheckoutSmokeConfig {
+  static const _providerPrefix = '--payment-checkout-smoke=';
+  static const _runIDPrefix = '--payment-checkout-run-id=';
+  static final _runIDPattern = RegExp(
+    r'^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-5][0-9a-fA-F]{3}-'
+    r'[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$',
+  );
+
+  final String provider;
+  final String runID;
+
+  const PaymentCheckoutSmokeConfig({
+    required this.provider,
+    required this.runID,
+  });
+
+  String get email => 'e2e+$runID@getlantern.org';
+
+  static PaymentCheckoutSmokeConfig? parse(
+    List<String> arguments, {
+    required bool isWindows,
+    required String buildType,
+  }) {
+    final providerArgument = _singleArgument(arguments, _providerPrefix);
+    final runIDArgument = _singleArgument(arguments, _runIDPrefix);
+
+    if (providerArgument == null && runIDArgument == null) {
+      return null;
+    }
+    if (!isWindows || buildType != 'nightly') {
+      throw const FormatException(
+        'Payment checkout smoke mode is available only in Windows nightly builds',
+      );
+    }
+    if (providerArgument == null || runIDArgument == null) {
+      throw const FormatException(
+        'Payment checkout smoke mode requires a provider and run ID',
+      );
+    }
+
+    final provider = providerArgument.toLowerCase();
+    if (provider != 'stripe' && provider != 'shepherd') {
+      throw FormatException('Unsupported payment checkout provider: $provider');
+    }
+    if (!_runIDPattern.hasMatch(runIDArgument)) {
+      throw const FormatException('Invalid payment checkout smoke run ID');
+    }
+
+    return PaymentCheckoutSmokeConfig(provider: provider, runID: runIDArgument);
+  }
+
+  static String? _singleArgument(List<String> arguments, String prefix) {
+    final matches = arguments.where((argument) => argument.startsWith(prefix));
+    if (matches.length > 1) {
+      throw FormatException('Argument may be specified only once: $prefix');
+    }
+    if (matches.isEmpty) {
+      return null;
+    }
+    final value = matches.single.substring(prefix.length).trim();
+    if (value.isEmpty) {
+      throw FormatException('Argument requires a value: $prefix');
+    }
+    return value;
+  }
+}
diff --git a/lib/core/widgets/app_webview.dart b/lib/core/widgets/app_webview.dart
index 16aeee0018..21b557a660 100644
--- a/lib/core/widgets/app_webview.dart
+++ b/lib/core/widgets/app_webview.dart
@@ -100,7 +100,10 @@ class _InnerWebViewState extends ConsumerState<_InnerWebView> {
       shouldOverrideUrlLoading: shouldOverrideUrlLoading,
       initialUrlRequest: _initialRequest,
       initialSettings: setting,
-      onWebViewCreated: (controller) {},
+      onWebViewCreated: (_) {
+        final uri = Uri.tryParse(widget.url);
+        _logSmokeEvent('created', uri);
+      },
       onCreateWindow: (controller, createWindowAction) async {
         final req = createWindowAction.request;
         if (PlatformUtils.isWindows) {
@@ -120,29 +123,92 @@ class _InnerWebViewState extends ConsumerState<_InnerWebView> {
         return false;
       },
       onLoadStart: (_, webUri) async {
-        // Handle load start
         final loading = ref.read(webViewLoadingProvider.notifier);
         loading.start();
+        _logSmokeEvent(
+          'load_start',
+          webUri == null ? null : Uri.tryParse(webUri.toString()),
+        );
       },
       onLoadStop: (controller, webUri) async {
-        // Handle load stop
         ref.read(webViewLoadingProvider.notifier).stop();
-        await _handleCompletionUrl(
-          webUri == null ? null : Uri.tryParse(webUri.toString()),
+        final uri = webUri == null ? null : Uri.tryParse(webUri.toString());
+        var documentLength = -1;
+        try {
+          final rawLength = await controller.evaluateJavascript(
+            source:
+                "(document.documentElement && document.documentElement.outerHTML || '').length",
+          );
+          final parsedLength = rawLength is num
+              ? rawLength.toInt()
+              : int.tryParse(rawLength.toString());
+          if (parsedLength == null) {
+            _logSmokeEvent(
+              'document_error',
+              uri,
+              detail: 'reason=invalid_document_length',
+            );
+          } else {
+            documentLength = parsedLength;
+          }
+        } catch (_) {
+          _logSmokeEvent(
+            'document_error',
+            uri,
+            detail: 'reason=evaluate_javascript_failed',
+          );
+        }
+        _logSmokeEvent(
+          'load_stop',
+          uri,
+          detail: 'document_length=$documentLength',
         );
+        await _handleCompletionUrl(uri);
       },
       onReceivedError: (_, webResourceRequest, error) async {
-        // Handle received error
-        appLogger.error("Received error: $error");
-        // Handle load stop
-        ref.read(webViewLoadingProvider.notifier).stop();
-        await _handleCompletionUrl(
+        final uri = Uri.tryParse(webResourceRequest.url.toString());
+        final isMainFrame = webResourceRequest.isForMainFrame == true;
+        appLogger.error(
+          'WebView request failed: type=${error.type} '
+          'main_frame=$isMainFrame host=${uri?.host ?? '<none>'}',
+        );
+        _logSmokeEvent(
+          isMainFrame ? 'navigation_error' : 'resource_error',
+          uri,
+          detail: 'error_type=${error.type}',
+        );
+        if (isMainFrame) {
+          ref.read(webViewLoadingProvider.notifier).stop();
+          await _handleCompletionUrl(uri);
+        }
+      },
+      onReceivedHttpError: (_, webResourceRequest, errorResponse) async {
+        if (webResourceRequest.isForMainFrame != true) return;
+        _logSmokeEvent(
+          'navigation_error',
           Uri.tryParse(webResourceRequest.url.toString()),
+          detail: 'http_status=${errorResponse.statusCode}',
         );
       },
     );
   }
 
+  void _logSmokeEvent(String event, Uri? uri, {String detail = ''}) {
+    if (!PlatformUtils.isWindows || AppBuildInfo.buildType != 'nightly') {
+      return;
+    }
+    // Checkout paths and query strings can contain session tokens. The origin
+    // is enough to prove which provider loaded without putting them in CI logs.
+    final safeUri = uri == null
+        ? '<none>'
+        : uri.replace(path: '', query: '', fragment: '').toString();
+    final suffix = detail.isEmpty ? '' : ' $detail';
+    appLogger.info(
+      'PAYMENT_WEBVIEW_SMOKE event=$event host=${uri?.host ?? '<none>'} '
+      'url=$safeUri$suffix',
+    );
+  }
+
   bool isLanternHost(String host) =>
       host == 'lantern.io' || host == 'www.lantern.io';
 
diff --git a/lib/features/auth/choose_payment_method.dart b/lib/features/auth/choose_payment_method.dart
index f5d988b6eb..f93ff11920 100644
--- a/lib/features/auth/choose_payment_method.dart
+++ b/lib/features/auth/choose_payment_method.dart
@@ -476,6 +476,7 @@ class PaymentCheckoutMethods extends HookConsumerWidget {
       padding: EdgeInsets.zero,
       itemBuilder: (context, index) {
         final method = providers[index];
+        final providerName = method.providers.name.toTitleCase();
         return Padding(
           padding: const EdgeInsets.only(bottom: 16),
           child: ExpansionTile(
@@ -498,15 +499,20 @@ class PaymentCheckoutMethods extends HookConsumerWidget {
               horizontal: defaultSize,
               vertical: defaultSize,
             ),
-            title: Row(
-              children: [
-                Text(
-                  method.method.replaceAll('-', " ").toTitleCase(),
-                  style: theme.titleMedium,
-                ),
-                SizedBox(width: defaultSize),
-                LogsPath(logoPaths: method.providers.icons),
-              ],
+            title: Semantics(
+              identifier: 'payment-provider-${method.providers.name}',
+              label: '$providerName payment method',
+              excludeSemantics: true,
+              child: Row(
+                children: [
+                  Text(
+                    method.method.replaceAll('-', " ").toTitleCase(),
+                    style: theme.titleMedium,
+                  ),
+                  SizedBox(width: defaultSize),
+                  LogsPath(logoPaths: method.providers.icons),
+                ],
+              ),
             ),
             children: [
               Row(
@@ -591,14 +597,19 @@ class PaymentCheckoutMethods extends HookConsumerWidget {
                 style: theme.bodySmall!.copyWith(color: context.textDisabled),
               ),
               SizedBox(height: defaultSize),
-              PrimaryButton(
-                label: method.providers.supportSubscription
-                    ? 'subscribe'.i18n
-                    : 'checkout'.i18n,
-                enabled: !isSubmitting,
-                onPressed: () {
-                  onSubscribe.call(method);
-                },
+              Semantics(
+                identifier: 'payment-checkout-${method.providers.name}',
+                label: 'Continue with $providerName',
+                excludeSemantics: true,
+                child: PrimaryButton(
+                  label: method.providers.supportSubscription
+                      ? 'subscribe'.i18n
+                      : 'checkout'.i18n,
+                  enabled: !isSubmitting,
+                  onPressed: () {
+                    onSubscribe.call(method);
+                  },
+                ),
               ),
             ],
           ),
diff --git a/lib/lantern_app.dart b/lib/lantern_app.dart
index e51555493e..95e91d5f8c 100644
--- a/lib/lantern_app.dart
+++ b/lib/lantern_app.dart
@@ -4,14 +4,17 @@ import 'dart:ui';
 import 'package:app_links/app_links.dart';
 import 'package:auto_route/auto_route.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/semantics.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:flutter_screenutil/flutter_screenutil.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:i18n_extension/i18n_extension.dart';
 import 'package:lantern/core/localization/localization_constants.dart';
 import 'package:lantern/core/router/router.dart';
+import 'package:lantern/core/smoke/payment_checkout_smoke.dart';
 import 'package:lantern/core/widgets/loading_indicator.dart';
 import 'package:lantern/features/home/provider/app_setting_notifier.dart';
+import 'package:lantern/features/plans/provider/plans_notifier.dart';
 import 'package:lantern/features/window/window_wrapper.dart';
 import 'package:lantern/lantern/lantern_service_notifier.dart';
 import 'package:loader_overlay/loader_overlay.dart';
@@ -25,7 +28,9 @@ final globalRouter = sl<AppRouter>();
 final RouteObserver<PageRoute> routeObserver = RouteObserver<PageRoute>();
 
 class LanternApp extends StatefulHookConsumerWidget {
-  const LanternApp({super.key});
+  final PaymentCheckoutSmokeConfig? paymentCheckoutSmoke;
+
+  const LanternApp({super.key, this.paymentCheckoutSmoke});
 
   @override
   ConsumerState<ConsumerStatefulWidget> createState() => _LanternAppState();
@@ -35,6 +40,7 @@ class _LanternAppState extends ConsumerState<LanternApp>
     with WidgetsBindingObserver {
   late final AppLifecycleListener _lifecycle;
   StreamSubscription<Uri>? _deepLinkSubscription;
+  SemanticsHandle? _paymentSmokeSemantics;
   Uri? _lastHandledUri;
   DateTime? _lastHandledTime;
 
@@ -44,6 +50,69 @@ class _LanternAppState extends ConsumerState<LanternApp>
     WidgetsBinding.instance.addObserver(this);
     initDeepLinks();
     initLifecycleListener();
+    if (widget.paymentCheckoutSmoke != null) {
+      // The Windows runner drives this screen through MSAA, so keep Flutter's
+      // semantic tree alive for the duration of the smoke.
+      _paymentSmokeSemantics = WidgetsBinding.instance.ensureSemantics();
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        unawaited(_openPaymentCheckoutSmoke(widget.paymentCheckoutSmoke!));
+      });
+    }
+  }
+
+  Future<void> _openPaymentCheckoutSmoke(
+    PaymentCheckoutSmokeConfig smoke,
+  ) async {
+    // Keep plans alive during startup retries. The payment screen starts
+    // watching them after navigation.
+    final plansSubscription = ref.listenManual(plansProvider, (_, _) {});
+    try {
+      final planData = await ref.read(plansProvider.future);
+      final matchingProviders = planData.providers.desktop.where(
+        (provider) => provider.providers.name == smoke.provider,
+      );
+      if (matchingProviders.isEmpty) {
+        throw StateError(
+          'Provider ${smoke.provider} is absent from staging desktop plans',
+        );
+      }
+      final provider = matchingProviders.first.providers;
+      final expectedSubscription = smoke.provider == 'stripe';
+      if (provider.supportSubscription != expectedSubscription) {
+        throw StateError(
+          'Provider ${smoke.provider} has unexpected subscription capability',
+        );
+      }
+      if (planData.plans.isEmpty) {
+        throw StateError('Staging returned no payment plans');
+      }
+
+      final selectedPlan = planData.plans.firstWhere(
+        (plan) => plan.bestValue,
+        orElse: () => planData.plans.first,
+      );
+      ref.read(plansProvider.notifier).setSelectedPlan(selectedPlan);
+      appLogger.info(
+        'PAYMENT_CHECKOUT_SMOKE event=ready provider=${smoke.provider} '
+        'run_id=${smoke.runID} plan=${selectedPlan.id} '
+        'billing=${expectedSubscription ? 'subscription' : 'one_time'}',
+      );
+      await appRouter.replaceAll([
+        ChoosePaymentMethod(
+          email: smoke.email,
+          authFlow: AuthFlow.renewSubscription,
+        ),
+      ]);
+    } catch (error, stackTrace) {
+      appLogger.error(
+        'PAYMENT_CHECKOUT_SMOKE event=bootstrap_error '
+        'provider=${smoke.provider} error=$error',
+        error,
+        stackTrace,
+      );
+    } finally {
+      plansSubscription.close();
+    }
   }
 
   void initLifecycleListener() {
@@ -64,6 +133,7 @@ class _LanternAppState extends ConsumerState<LanternApp>
     WidgetsBinding.instance.removeObserver(this);
     _lifecycle.dispose();
     _deepLinkSubscription?.cancel();
+    _paymentSmokeSemantics?.dispose();
     super.dispose();
   }
 
diff --git a/lib/main.dart b/lib/main.dart
index da502724ea..62cfb2b625 100644
--- a/lib/main.dart
+++ b/lib/main.dart
@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:io';
 
 import 'package:device_info_plus/device_info_plus.dart';
 import 'package:flutter/foundation.dart';
@@ -10,6 +11,7 @@ import 'package:flutter_timezone/flutter_timezone.dart';
 import 'package:lantern/core/common/common.dart';
 import 'package:lantern/core/desktop/desktop_window.dart';
 import 'package:lantern/core/services/injection_container.dart';
+import 'package:lantern/core/smoke/payment_checkout_smoke.dart';
 import 'package:lantern/core/updater/updater.dart';
 import 'package:lantern/core/utils/storage_utils.dart';
 import 'package:lantern/lantern_app.dart';
@@ -17,7 +19,7 @@ import 'package:package_info_plus/package_info_plus.dart';
 import 'package:timezone/data/latest_all.dart' as tz;
 import 'package:timezone/timezone.dart' as tz;
 
-Future<void> main() async {
+Future<void> main([List<String> arguments = const []]) async {
   WidgetsFlutterBinding.ensureInitialized();
 
   // Timezone is only needed for notification scheduling (data-cap alerts),
@@ -39,6 +41,15 @@ Future<void> main() async {
     final flutterLog = await AppStorageUtils.flutterLogFile();
     initLogger(flutterLog.path);
     appLogger.debug('Starting app initialization...');
+    if (PlatformUtils.isWindows && AppBuildInfo.buildType == 'nightly') {
+      // The Windows runner sets this before Dart starts. If it is unset,
+      // WebView2 did not get its per-user folder.
+      appLogger.info(
+        'WEBVIEW2_DIAGNOSTIC user_data_folder='
+        '${Platform.environment['WEBVIEW2_USER_DATA_FOLDER'] ?? '<unset>'} '
+        'local_app_data=${Platform.environment['LOCALAPPDATA'] ?? '<unset>'}',
+      );
+    }
     unawaited(_logDeviceInfo());
     await _loadAppSecrets();
     appLogger.debug('Injecting services...');
@@ -64,10 +75,33 @@ Future<void> main() async {
     appLogger.error('Failed to start Updater.init', e, st);
   }
 
+  PaymentCheckoutSmokeConfig? paymentCheckoutSmoke;
+  try {
+    paymentCheckoutSmoke = PaymentCheckoutSmokeConfig.parse(
+      arguments,
+      isWindows: PlatformUtils.isWindows,
+      buildType: AppBuildInfo.buildType,
+    );
+    if (paymentCheckoutSmoke != null) {
+      appLogger.info(
+        'PAYMENT_CHECKOUT_SMOKE event=enabled '
+        'provider=${paymentCheckoutSmoke.provider} '
+        'run_id=${paymentCheckoutSmoke.runID}',
+      );
+    }
+  } on FormatException catch (error, stackTrace) {
+    appLogger.error(
+      'PAYMENT_CHECKOUT_SMOKE event=rejected error=$error',
+      error,
+      stackTrace,
+    );
+    rethrow;
+  }
+
   runApp(
     ProviderScope(
       retry: (retryCount, error) => null,
-      child: const LanternApp(),
+      child: LanternApp(paymentCheckoutSmoke: paymentCheckoutSmoke),
     ),
   );
 }
diff --git a/test/core/smoke/payment_checkout_smoke_test.dart b/test/core/smoke/payment_checkout_smoke_test.dart
new file mode 100644
index 0000000000..7006e84e05
--- /dev/null
+++ b/test/core/smoke/payment_checkout_smoke_test.dart
@@ -0,0 +1,84 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:lantern/core/smoke/payment_checkout_smoke.dart';
+
+void main() {
+  group('PaymentCheckoutSmokeConfig', () {
+    test('does nothing without smoke arguments', () {
+      expect(
+        PaymentCheckoutSmokeConfig.parse(
+          const [],
+          isWindows: true,
+          buildType: 'nightly',
+        ),
+        isNull,
+      );
+    });
+
+    test('accepts a constrained provider and derives the E2E email', () {
+      final config = PaymentCheckoutSmokeConfig.parse(
+        const [
+          '--payment-checkout-smoke=stripe',
+          '--payment-checkout-run-id=9a1632f8-5b33-4d6f-8a42-7a8a4f77d829',
+        ],
+        isWindows: true,
+        buildType: 'nightly',
+      );
+
+      expect(config?.provider, 'stripe');
+      expect(
+        config?.email,
+        'e2e+9a1632f8-5b33-4d6f-8a42-7a8a4f77d829@getlantern.org',
+      );
+    });
+
+    test('rejects the hook outside a Windows nightly build', () {
+      expect(
+        () => PaymentCheckoutSmokeConfig.parse(
+          const [
+            '--payment-checkout-smoke=stripe',
+            '--payment-checkout-run-id=9a1632f8-5b33-4d6f-8a42-7a8a4f77d829',
+          ],
+          isWindows: true,
+          buildType: 'production',
+        ),
+        throwsFormatException,
+      );
+    });
+
+    test('rejects arbitrary providers and malformed run IDs', () {
+      expect(
+        () => PaymentCheckoutSmokeConfig.parse(
+          const [
+            '--payment-checkout-smoke=https://example.com',
+            '--payment-checkout-run-id=9a1632f8-5b33-4d6f-8a42-7a8a4f77d829',
+          ],
+          isWindows: true,
+          buildType: 'nightly',
+        ),
+        throwsFormatException,
+      );
+      expect(
+        () => PaymentCheckoutSmokeConfig.parse(
+          const [
+            '--payment-checkout-smoke=shepherd',
+            '--payment-checkout-run-id=../../unsafe',
+          ],
+          isWindows: true,
+          buildType: 'nightly',
+        ),
+        throwsFormatException,
+      );
+      expect(
+        () => PaymentCheckoutSmokeConfig.parse(
+          const [
+            '--payment-checkout-smoke=',
+            '--payment-checkout-run-id=9a1632f8-5b33-4d6f-8a42-7a8a4f77d829',
+          ],
+          isWindows: true,
+          buildType: 'nightly',
+        ),
+        throwsFormatException,
+      );
+    });
+  });
+}